The present invention relates to devices for heat spreading and dissipation in electronic systems and, more particularly to heat dissipation devices useful for conducting heat away from semiconductor chips and their carriers, including land grid arrays.
The performance of electronic circuits and their semiconductor devices is limited by temperature. Semiconductor device performance degrades when the internal temperature reaches or exceeds a particular limit. That limit depends upon the nature of the semiconductor device. There are often numerous semiconductor-related heat sources 2 within a typical electronic device, e.g., a central processing unit or xe2x80x9cCPUxe2x80x9d 2 (FIG. 1). Other active semiconductor devices 3 that are mounted to a printed circuit or wiring board (PCB 4) and even the current flowing through the circuit traces 5, the connection device between CPU 2 and PCB 4 (the chip carrier, interposer, etc.,) generate thermal energy.
In order to maintain or increase the performance of such devices, they must be cooled in some way. The manner of cooling depends upon many parameters, including the space available for the cooling process, the temperatures to be encountered, etc. In some instances simply passing a fluid over the device or, over a finned heat sink that is attached to the device, is sufficient to maintain the semiconductor at safe operating temperatures. In one known semiconductor device cooling technique, convecting fins are attached to a semiconductor package, or the package is affixed to a larger metal member, referred to as a heat sink or cold plate. This heat sink draws heat away from the semiconductor device and can be air-cooled or liquid cooled, depending upon the particular application. If the heat sink is air-cooled it will typically have heat convecting fins.
Modern electronics equipment includes various active, heat-generating semiconductor components that require the use of connection devices for electrical connection with a PCB. As is known in the art, xe2x80x9cland grid arraysxe2x80x9d (LGA""s) or xe2x80x9cpin grid arraysxe2x80x9d (PGA""s) are examples of such connection devices, and are used when the active component to be connected has a plurality of contacts that are arranged in a regular pattern. Another connection device, known as an xe2x80x9cinterposer,xe2x80x9d connector (identified generally by reference numeral 6 in FIG. 1) typically comprises an array of contacts, elements, or pads supported in a flat housing so as to protrude from the top and bottom surfaces. Interposer 6 is placed between the active component 2 and PCB 4, or between two PCB""s, and provides electrical connection between correspondingly positioned contact pads. LGA interposers described in the prior art may often include springs or conductive buttons inserted into an array of appropriately located holes in an insulating housing.
For example, in U.S. Pat. No. 6,264,476, incorporated herein by reference, an interposer for an LGA is disclosed that includes a dielectric housing having an array or grid of holes and a resilient, conductive button disposed in one or more of the holes. In U.S. Pat. No. 6,312,266, also incorporated herein by reference, a carrier is disclosed that provides improved retention to the individual contact elements resulting in an LGA interposer connector with improved manufacturability, reliability and more uniform mechanical and electrical performance. In one embodiment, the carrier includes upper and lower sections of dielectric material with an adhesive layer in between. Other prior art that may be relevant includes U.S. Pat. Nos. 5,528,456; 5,705,850; 6,299,460; 6,304,451; 6,078,500; and 6,317,326.
Numerous electronics systems require more and more current to be delivered through a connector and chip carrier to an array of semiconductor devices. This is especially true with current technology motherboards whose processors are clocked at speeds exceeding one gigahertz. For example, in each new generation of microprocessor, a greater number of transistors are packed onto each die, generating significantly more heat, and making the package thermal resistance critical. Furthermore, the trend toward shrinking semiconductor die sizes has caused higher power density, which strains the effectiveness of the package to dissipate heat.
There is a need in the art for an LGA interposer connector with improved manufacturability, reliability and more uniform mechanical and electrical performance, and that also provides enhanced thermal management capability through efficient heat transfer characteristics.
The invention provides a heat spreading interposer suitable for use with electronic components including those using land grid arrays and pin grid arrays. In one embodiment of the heat spreading interposer at least one electrical contact element is supported by a housing comprising a laminate. The laminated housing includes at least one layer of thermally conductive material supported by at least one layer of a dielectric material so that a portion of the at least one electrical contact element is in thermal communication with the at least one layer of thermally conductive material.
In another embodiment of the invention, a heat spreading interposer is provided including a plurality of electrical contact elements each having a first end and a second end. The electrical contact elements are supported by a housing so that the first end projects outwardly from a first side of the housing and the second end projects outwardly from a second side of the housing. The housing is formed from at least one layer of thermally conductive material supported by at least one layer of a dielectric material so that a portion of each of the plurality of electrical contact elements is in thermal communication with the at least one layer of thermally conductive material. In one aspect of the invention, the dielectric material comprises an injection molded polymer disposed in substantially surrounding relation to a lead frame that forms the at least one layer of thermally conductive material.
A method of spreading heat in an connection device is also provided in which an interposer is provided that comprises a plurality of electrical contacts supported by a housing. The housing is formed from at least one layer of thermally conductive material positioned between two layers of a dielectric material so that a portion of each of the plurality of electrical contacts is in thermal communication with the at least one layer of thermally conductive material. The interposer is positioned intermediate of an electronic device and a printed circuit board to conduct heat away from the electronic device and other heat generating components through the at least one layer of thermally conductive material.